Infrared laser image/video transfer

Discussion in 'General Electronics Chat' started by Stephen Kabali, Feb 25, 2018.

  1. Stephen Kabali

    Thread Starter New Member

    Feb 25, 2018
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    Hello, does anyone know or has anyone done data(image/video) transfer via infrared laser?
    I have transmitted music but not been able to transfer, please help
     
  2. RichardO

    Late Member

    May 4, 2013
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    What kind of video? NTSC or something else?
     
  3. Stephen Kabali

    Thread Starter New Member

    Feb 25, 2018
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    0
    yes, NTSC is just fine.
     
  4. RichardO

    Late Member

    May 4, 2013
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    What have you tried?

    The main difference between audio and video is the frequencies involved. For NTSC you need about 5 MHz of bandwidth. This is almost 1000 times higher than audio.

    The receiver for video must be able to drive a 50 ohm load whereas audio reciever only needs to drive a 10 K ohm load.

    By the way, there are products made to do what you want over fiber optic links.
     
  5. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    75 ohm.

    For a simple experiment you can amplitude-modulate the laser beam intensity, but for any kind of quality you will need an extremely linear FM modulator. Broadcast quality color videotape started in 1957 with a carrier frequency range of 5.5 to 6.5 MHz. Yes, 4 MHz information on a 6 MHz carrier. Yes, it worked.

    Things evolved up to High-band color in the 60's using a 10 MHz carrier, still a very poor modulation index. They got away with it because the noise floor of the tape was so high that a higher carrier frequency did not improve the quality of the recovered signal. With the components and tech that are available today, I'd start up around 20 MHz.

    ak
     
    Last edited: Feb 28, 2018
  6. RichardO

    Late Member

    May 4, 2013
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    Yes 75 ohms, not 50. :oops:

    I have never modulated a diode Laser. Do you have any feel for how fast a typical Laser, such as a Laser pointer, can be modulated? I've heard of some gas Lasers being modulated at as high as 100 MHz. :eek:
     
  7. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    Laser diodes run the core of the internet at gigahertz speeds, but they cost more than a laser pointer. A 10-cent red LED turns on in about 10-20 ns and off in 50 ns (working from memory).

    In the 70's I worked nights at a TV station. We cannibalized an old videotape machine are replaced 100% of the electronics with contemporary circuits. Once we had the mod and demod working, we whipped up a visible LED link between the two (yup, bored). It worked well enough to show off.

    ak
     
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